Galaxies and galaxy clusters can magnify objects at cosmic distances by large factors. To first order the maximum possible magnification depends on i) the mass of the lens and ii) the size of the background object. Small objects, like stars, can be magnified by factors of several thousand when the lens is a galaxy cluster. Kelly et al. 2018 discovered the first star at cosmological distance magnified by such extreme factors. I will show how the properties of the magnification can be altered by intervening microlenses (from the macrolens) and how this can be used to constrain the amount of dark matter that is in compact form. Gravitational Waves (GW) are another example, where the signal originates from an incredibly small source. I will show how the most massive events detected by LIGO can be re-interpreted as strongly lensed events at z~1-2 by groups of galaxies or small clusters at z~0.3.